Science Matters: Can you give us a quick overview of EPA's air, climate, and energy research? Why is EPA studying these issues together as a unified program?

Dr. Dan Costa: I think that's a great question.

Over time, it's become increasingly clear that these issues—air pollution, climate change, and energy production and use—are deeply intertwined.

Our choices in energy, whether it's fossil fuels, or wind or solar, have implications for air quality and climate change; and climate change impacts local air quality, as well as our energy infrastructure. So it's very logical, if we're ever going to really make headway, that we look at these issues in a comprehensive and interactive, systems-based manner.

Science Matters: Over 40 years of research, what kind of advances have we made with respect to air pollution, and what are the challenges we're still facing?

Dr. Dan Costa: There have been great strides since the passage of the Clean Air Act in the 70s, almost to the point now, when we look outside, the air is clear in most places—even in most urban environments—and we kind of forget the fact that there are things in the air that while we can't see them we can inhale them.

When the Clean Air Act was first passed, while we knew air pollution was a big mixture, we couldn't understand the multiple-pollutant environment. So, we looked at what were the most ubiquitous and important pollutants that would likely have a health impact—the so called 'criteria pollutants' (ozone, particulate matter, etc.), and we focused our studies on those.
Since then, overall pollution levels have decreased some 85%. For example, the automobile produces just a few percentage points of the emissions that it did in 1970. Industry also figured out that by being more efficient and reducing pollution, they were in fact pushing their own positive economies.

And yet there are 120 million people in the U.S. living in areas that are still out-of-compliance with today's pollution standards.

We've been able—through sensitive testing procedures, evaluations, and risk assessment—to see that there are people who are affected by low levels of pollution, especially over long periods of time.

There are a number of issues that we still have to deal with in achieving the American ideal.

Dr. Dan Costa

Science Matters: Much of your research has been focused on working toward a "one-atmosphere" model. Can you elaborate on what you mean by that?

Dr. Dan Costa: "One atmosphere" is part of our systems thinking. We know air pollution is a complex mix of pollutants. It's not just the six criteria pollutants. Air pollution varies by location, source, meteorology, atmospheric chemistry, and other factors.

We know that the world is 80% water; we know the land is a constant dynamic of vegetative changes; we know that certain pollutants that derive from nitrogen deposit on soil and water and have an impact on plants.

All of these systems are interlinked, and our visionary goal is to start to pull together these compartmentalized models and bridge them into a "one-environment model."

We've gone about as far as we can trying to do things on a pollutant-by-pollutant basis, so we need to look at the whole atmosphere in assessing risk. How does an individual pollutant behave in a complex mix? How does the mix change as we reduce that individual pollutant?

It's not going to be simple. And, for the sake of accessibility for our partners and local decision makers, we don't want a model that requires a supercomputer to run.

Science Matters: How does EPA modeling support the work of environmental decision-makers?

Dr. Dan Costa: Air pollution models, and many other kinds of models developed by EPA and its partners, are used daily by environmental managers, scientists, and government decision-makers at the state, local, and community levels.

The question is: How can we look at these air, climate, and energy issues in a dynamic and predictive way so that these leaders can make informed decisions?

What's the impact if we reduce this emission? Does it affect something else? Everything has alternative consequences. Some can be negative; some can be positive. We like the idea of co-benefits; for example, reducing black carbon from cookstoves has a public health benefit and a climate change co-benefit.

Models help us maximize these synergies and deliver the biggest environmental bang for the buck that we can. We know from our history that—if we're strategic and we think and apply ourselves appropriately with a cooperative effort—we can have both environmental protection and a robust economy.